Combined Research of Dispersed Precipitates in High-Strength Steel

Abstract

Disperse precipitates in high-strength high-chromium martensite-ferrite steel of 0.15C–12Cr–Ni–Mo–W–V composition after various modes simulating the after-forging annealing were investigated. The investigated metal after holding at 1050°С for 1 h and quenching in oil was heat treated (HT) in two modes: HT 1—the after-forging annealing at 700°С for 6 h to relieve stresses; HT 2—HT 1 with the following isothermal annealing, heating to 1000°С, short holding, cooling to 700°С, and holding for 16 h. On the basis of the combined research, including optical metallography, X-ray phase analysis, transmission electron microscopy, and small-angle X-ray scattering, it was found that the tempered martensite structure with the ferrite phase of less than 1% was formed in the steel after HT 1; and after HT 2, transition from the martensiteferrite to ferrite-pearlite state took place; significant growth of carbides of the (Fe Cr)23C6 type and substructural components (coherent scattering areas, electron density inhomogeneity) was found; and finely dispersed particles of vanadium carbide V2C about 30 nm in size were formed.